Installation comprising an articulated arm and a machine tool, and corresponding machining method

Abstract

A machining apparatus is borne by an articulated arm and includes: a casing defining an opening to be placed by the articulated arm in a machining position so the opening faces the surface to be machined; at least three bearers attached to the casing to rest against the surface to be machined in the machining position; an attachment system fixing the casing to the surface to be machined; at least one support mounted to move with respect to the casing, and a machine-tool mounted on the support; and at least one position sensor providing position parameters representing a relative position of the surface to be machined with respect to the casing. Also included is a control system operating the support and to move the machine-tool with respect to the casing according to a movement instruction, the control system being designed to calculate the movement instruction using the position parameters.

The invention claimed is: 
     
       1. An installation for machining an object defining a surface that is to be machined, the installation comprising an articulated arm, and a machine tool borne by the articulated arm and comprising:
 a housing defining at least one opening and intended to be placed by the articulated arm in a machining position in which the opening is situated facing the surface that is to be machined, 
 at least three bearers secured to the housing and intended to bear against the surface that is to be machined in the machining position, 
 an attachment system for fixing the housing to the surface that is to be machined, 
 at least one support mounted with the ability to move with respect to the housing, and a machining tool designed to be mounted on the support, and 
 at least one position sensor designed to provide position parameters indicative of a relative position of the surface that is to be machined with respect to the housing, 
 the installation further comprising a control system designed to actuate the support and move the machining tool with respect to the housing according to a movement instruction, the control system being designed to calculate the movement instruction using the position parameters, 
 wherein the at least three bearers are respectively equipped with strain gauges designed to measure pressure forces exerted respectively by the at least three bearers on the surface that is to be machined, 
 the control system being designed to bring a first of the at least three bearers into contact with the surface that is to be machined and then bring a second of the at least three bearers into contact, with the first of the at least three bearers remaining in contact, and then bring a third of the at least three bearers into contact, with the first and the second of the at least three bearers remaining in contact, 
 wherein each of the bringings into contact is performed in such a way that the corresponding pressure force progressively reaches a predetermined value. 
 
     
     
       2. The installation according to  claim 1 , in which the attachment system comprises at least three suction cups secured to the housing and designed to be pressed against the surface that is to be machined in the machining position, and a vacuum source selectively creating a vacuum between the suction cups and the surface that is to be machined. 
     
     
       3. The installation according to  claim 2 , in which the at least three bearers are respectively situated substantially in the middle of the at least three suction cups. 
     
     
       4. The installation according to  claim 1 , in which the machine tool further comprises at least three telemeters designed to respectively provide at least three distance parameters, each distance parameter being respectively indicative of a distance between one of the telemeters and the surface that is to be machined. 
     
     
       5. The installation according to  claim 1 , further comprising at least one probe designed to be mounted on the support, the control system being designed to move the support and the probe in order to probe the surface that is to be machined and calculate shape parameters indicative of a shape of the surface that is to be machined, the control system being further designed to calculate the movement instruction for the machining tool to take account of the shape parameters. 
     
     
       6. The installation according to  claim 5 , wherein the at least one probe is designed to be mounted on the support at substantially the same point as the machining tool. 
     
     
       7. The installation according to  claim 5 , further comprising a magazine designed to accept the probe or the machining tool in respective storage positions. 
     
     
       8. The installation according to  claim 1 , wherein the object is part of an aeroplane wing. 
     
     
       9. The installation according to  claim 1 , wherein the surface that is to be machined is the perimeter of an inspection hole. 
     
     
       10. A method for machining an object, the object defining a surface that is to be machined, the method comprising the following steps:
 provision of an articulated arm, of a machine tool borne by the articulated arm, and of a control system, the machine tool comprising a housing defining at least one opening, at least three bearers secured to the housing, an attachment system, at least one support mounted with the ability to move with respect to the housing, a machining tool and at least one position sensor mounted on the support; 
 mounting of the machining tool on the support; 
 placement of the housing, by the articulated arm, in a machining position in which the opening is situated facing the surface that is to be machined, the placement involving applying the at least three bearers against the surface that is to be machined; 
 fixing of the housing on the surface that is to be machined using the attachment system; 
 provision, by the position sensor, of position parameters indicative of a relative position of the surface that is to be machined with respect to the housing in the machining position; 
 calculation, by the control system, of a movement instruction for the machining tool, using the position parameters; and 
 actuation, by the control system, of the support and movement of the machining tool with respect to the housing in accordance with the calculated movement instruction, 
 the method, in which, as the at least three bearers are applied to the surface that is to be machined, strain gauges measure pressure forces exerted respectively by the at least three bearers on the surface that is to be machined, and in which, as the housing is fixed to the surface that is to be machined, suction cups are applied to the surface that is to be machined, 
 the method further comprising a bringing of a first of the at least three bearers into contact with the surface that is to be machined and then a bringing of a second of the at least three bearers into contact, with the first of the at least three bearers remaining in contact, followed by a bringing of a third of the at least three bearers into contact, with the other first and second of the at least three bearers remaining in contact, 
 wherein each of the bringings into contact is performed in such a way that the corresponding pressure force progressively reaches a predetermined value. 
 
     
     
       11. The method according to  claim 10 , in which:
 the machine tool provided comprises at least three telemeters; 
 the placement of the housing involves provision of at least three distance parameters by the telemeters respectively, each distance parameter being respectively indicative of a distance between one of the telemeters and the surface that is to be machined. 
 
     
     
       12. The method according to  claim 11 , in which the placement of the housing involves:
 in a housing approach phase, a calculation, by the control system, of at least one parameter indicative of an orientation of the housing with respect to the surface that is to be machined, the calculation using the distance parameters; a controlling of the articulated arm by the control system to take account of the orientation parameter; and optionally a use of the position sensor, a calculation of at least one parameter pertaining to the position of the housing with respect to the surface that is to be machined and a controlling of the articulated arm by the control system in accordance with the position parameter. 
 
     
     
       13. The method according to  claim 10 , further comprising:
 a mounting of a probe on the support; and 
 after the placing of the housing in the machining position, a probing of the surface that is to be machined involving: a moving of the support and of the probe with respect to the housing by the control system; and a calculation, by the control system, of shape parameters indicative of a shape of the surface that is to be machined; 
 the calculation of the movement instruction for the machining tool by the control system using the shape parameters. 
 
     
     
       14. The method according to  claim 13 , in which:
 the probing takes place after the fixing of the housing to the surface that is to be machined and before the mounting of the machining tool on the support; and 
 the housing remains fixed to the surface that is to be machined during the mounting of the machining tool on the support. 
 
     
     
       15. The method according to  claim 14 , wherein the machine tool comprises a magazine designed to accept the probe or the machining tool in respective storage positions. 
     
     
       16. The method according to  claim 13 , in which, after probing, the housing is moved away from the surface that is to be machined by the articulated arm, the probe is dismantled from the support, then the machining tool is mounted on the support and the housing is positioned again in order to return the housing to the machining position. 
     
     
       17. The method according to  claim 13 , further comprising mounting the probe on the support at substantially the same point as the machining tool. 
     
     
       18. The method according to  claim 10 , wherein the object is a part of an aeroplane wing. 
     
     
       19. The method according to  claim 10 , wherein the surface that is to be machined is the perimeter of an inspection hole.